Tag axle systems are known in which an auxiliary axle with wheels attached thereto is moved to its stored, unengaged position and lowered in an engaged load bearing position to provide auxiliary axle and wheels for a load bearing vehicle. The tag axle must be stable and positionable for ground engagement, and movable to a second stored or transport position. In the transport position, the extra or auxiliary wheels should not interfere with the other functions of the vehicle.
One such tag axle system is illustrated in U.S. Pat. No. 4,146,243, issued Mar. 27, 1979 in the name of Sims. This patent discloses a linkage tag axle system wherein a power actuator rotates the linkage and a beam to bring the wheels into ground engaging position and a second power actuator pivots the beams upwardly to raise the wheels and tire set.
A simplified suspension system is illustrated in U.S. Pat. No. 3,743,315, issued Jul. 3, 1973 in the name of Bilas. This system discloses an auxiliary wheel and axle assembly for a trailer vehicle. A semi-elliptic spring positioned transversely of the vehicle is secured thereto and to the wheels and axle assembly. The spring lifts the assembly from a road surface. Air bags positioned between the wheel and axle assembly and the vehicle permit the wheel and axle assembly to be lifted from the road surface by the semi-elliptic spring or engaged on the road surface in a weight carrying relation to the trailer vehicle when the air bags are inflated.